The present invention relates to multistage push-button switches used, for example, in the operation of cranes and hoists, and more specifically to a detent or retaining mechanism for a push button that provides for temporary stopping thereof at prescribed intermediate positions when the push button of a push-button switch is pressed down.
As a retaining mechanism for a push button providing temporarily stoppage thereof at prescribed intermediate positions when the push button of a push-button switch is pressed down, the conventional type mechanism that is widely used is illustrated in FIG. 18 and includes steel balls 12 pressed apart by a spring 11 in a push button 3 forward one of plural stepped parts 16 spaced in an axial direction of movement of push button 3 and formed on opposite inner wall faces of switch body 1. Push button 3 is retained at a prescribed pressed position by steel balls 12 being retained at a particular step 16 when the push button 3 is pressed down, as shown in FIG. 18.
In such mechanism of conventional push buttons, the stepped part 16 must be formed in the shape of tapered steps because the switch body 1 is made of synthetic resin. For that reason, the more the push button 3 is pressed down, the greater the pressing force on the spring 11, making it impossible to maintain a constant pressing force of the clipped push button 3. As a result, this arrangement has poor durability, since when pressing the push button 3 the force required to move from a first step 16 to a second step 16 and from the second step 16 to a third step 16 becomes extremely large. Thus, the stepped parts 16 are liable to become worn by contact with the steel balls 12.